nfp: flower-ct: check for error in nfp_fl_ct_offload_nft_flow()

The nfp_fl_ct_add_flow() function can fail so we need to check for
failure.

Fixes: 95255017 ("nfp: flower-ct: add nft flows to nft list")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: NLouis Peens <louis.peens@corigine.com>
Reviewed-by: NSimon Horman <simon.horman@corigine.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/flower/conntrack.c

@@ -1067,6 +1067,8 @@ nfp_fl_ct_offload_nft_flow(struct nfp_fl_ct_zone_entry *zt, struct flow_cls_offl
 						    nfp_ct_map_params);
 		if (!ct_map_ent) {
 			ct_entry = nfp_fl_ct_add_flow(zt, NULL, flow, true, extack);
+			if (IS_ERR(ct_entry))
+				return PTR_ERR(ct_entry);
 			ct_entry->type = CT_TYPE_NFT;
 			list_add(&ct_entry->list_node, &zt->nft_flows_list);
 			zt->nft_flows_count++;